Sounds liek my daughter acted when she had reflux - smaller more frequent feedings are etter for them. They will lots of time sleep better, propped up - try the car-seat carrier, the swing or the bouncy seat. Don't force her to hear more than she wants, babies know when they are full, their little tummies are still TINY at this point, and if you over-fill it, she is more likely to have it back up into her throat, causing the fussing and spitting up. I would talk to your ped about it - make sure she is growing fine and gaining weight, and then let your baby lead with how much/often she needs to eat.
Girls and boys are just different, every kid is, so try not to compare them, she sounds JUST Like my little girl was, though she was breastfed, we got her on Infant Prevacid granules and that helped alot with the spitting up and crying. BUT even up tot 12 months, she rarely ever at over 4-5 ounces per bottle, even once she was on all formula. Asa 6 week old she ate ever 2 hours and she would take 45 minutes plus to nurse, and then when she slept it was for short fitful bursts, she fianlly slept through the night at 9 months after she was weaned to all formula. We did have to let her cry it out at that point. We followed the "Helathy Sleep Habits, Happy Child" book, by Dr. Marc Weissbluth.....BUT that said, all you can do when they are this little is make sure you put them down less than 2 hours after they get up, and follow a soothing routine, and make sure the room they sleep in is dark, and quiet - use white noise to block out outside sounds, and room darkenting curtains or shades. You can't do cry it out method of sleep training till after 4 months, sometimes later, depending on the child's temperment.
Good Luck! Every one is so different, you feel like you are starting all over again, learing to take care of each baby!
Jessie